Two oil tankers flying the flag of Antigua and Barbuda have been swept up in the latest round of U.S. sanctions against the Iran-backed Houthi movement, raising questions about how vessels under the twin-island state’s registry became entangled in a global smuggling and financing scheme.

The tankers, the Shria and the Nobel M, were identified by the U.S. Department of the Treasury as part of a network of ships managed by Tyba Ship Management DMCC, a UAE-based company linked to Houthi-affiliated businessman Muhammad Al-Sunaydar. Washington says the vessels have been used to discharge oil at the Houthi-controlled Ras Isa port, generating revenue that helps fund the group’s military activities, including missile and drone attacks in the Red Sea.

The sanctions, announced this week, target 32 individuals and entities, along with four tankers flagged under multiple jurisdictions. In addition to the Antiguan-registered vessels, the Star MM sails under the Barbados flag and the Black Rock under Panama’s.

U.S. officials allege that the shipping network supports the Houthis’ procurement of advanced weapons components from ballistic missile and cruise missile parts to unmanned aerial vehicle systems that have been used in attacks on American forces, regional allies, and international commercial traffic.

The presence of Antigua and Barbuda’s flag in the sanctions list highlights the risks faced by smaller maritime registries when foreign companies exploit open-flag systems. It is not yet clear whether the Antigua and Barbuda Department of Marine Services and Merchant Shipping (ADOMS), which oversees the country’s ship registry, will take independent action in response to the U.S. measures.

Antigua and Barbuda has long marketed its registry as a reputable international flag state, but the Treasury designation raises potential reputational and regulatory concerns. Maritime industry experts say flag states often depend on ship management companies to conduct due diligence, a system that can leave registries exposed when vessels are later tied to sanctioned activities.

For now, both the Shria and the Nobel M are expected to face restrictions on international operations, with banks, insurers, and port authorities likely to avoid dealings with the sanctioned ships.

The government of Antigua and Barbuda has not yet issued a statement regarding the U.S. announcement.